Industrial and medical gas company Air Liquide’s 
oxygen solutions and the Air Liquide dissolved oxygen control (Aldoc) system offer competitive pricing, good quality and service, reduced cyanide consumption, improved kinetics, and much 
improved recoveries to gold mines.

Air Liquide metallurgy manager Kobus Durand says that the response the company is getting from clients, such as AngloGold, Harmony Gold, Rand Gold Resources and the DRD Group, indicates that the Aldoc system is the preferred method of 
recovering gold in South Africa. Air Liquide designed the system in South Africa and is currently using it in several African countries, as well as in a few other countries, such as Thailand and Canada.

“The system is a complete package, which includes the supply of the injection system, the monitoring of oxygen injection with the continuous measurement of dissolved oxygen, the supply of oxygen and the associated expertise,” says Durand.

He adds that the benefits are recognised by the company’s clients as a revolutionary alternative to the old way of gold 
recovery, which involved peroxide and the simple injection of compressed air. This process was 
hazardous and detrimental to the 
environment. 
The Aldoc system is particularly environment friendly as part of its process includes the destruction of cyanide.

Air Liquide also provides the mining industry with shear 
reactors on refractory sulphides, which assist with oxidisation.

“The treatment of refractory 
sulphides with shear reactors 
allows sulphide oxidation to occur concurrently with the gold dissolution. 
“Once the gold solution is separated from the oxidised mineral slurry, the dissolved gold can be recovered by 
adsorption onto active carbon, which is subsequently diluted with cyanide for the ultimate 
recovery of the gold. The system yields an improved gold recovery from the slurry,” Durand asserts.

The company’s oxygen is also used in the treatment of effluent and preoxidation in the mining industry.